1. Field of Invention
The invention relates to a method for registering a rotary press comprising several inking systems.
2. Description of the Prior Art
Registering methods have been disclosed in the prior art. It is possible to differentiate between longitudinal registration and transverse registration depending on the effect of the registration corrections on the webs of material to be printed. Particularly the development of the direct drive technology, which assigns at least one independent drive that can be controlled individually to each cylinder carrying printing plates, has revolutionized the possibilities of the registering methods. The provision of affordable sensor systems or camera systems has decisively improved the possibilities of providing measured values even during the printing process.
Another possibility of differentiating between registering methods according to the prior art calls for the examination of the reference values, which are consulted for determining the deviation of the position of the printed images from their desired position. This possibility of differentiating between registering methods can be used to distinguish between web-web methods and web-cylinder methods. In web-web methods (e.g., DE 199 17 773 A1), the positions of parts of monochrome printed images on the material to be printed that are already printed one on top of the other, thus forming an already polychrome printed image, are compared to one another. Usually, these parts of monochrome printed images are registration marks, which are printed particularly for this purpose by each inking system. Based on the determined deviation of the position of the printed images from their desired position, correction signals are produced, which actuate the drives of the printing plate cylinders until the deviation of the positions of their monochrome printed images on the material to be printed lies within a range of tolerances. One of the weak points of this method is that no registration can be effected if registration marks are printed one on top of the other. In the web-cylinder method (e.g., DE 42 18 760 A1), it is sufficient to scan the position of a monochrome printed image—usually a registration mark—however, once for every inking system. The position of this registration mark at a point in time is then related to information on the rotary movement of the respective printing plate cylinder. This information is usually present in the form of trigger signals, which are provided by rotary transducers or simple switching devices. In this method, the position of the registration mark on the moving material to be printed at a point in time is related to the input of the trigger signals, in order to determine the correction signals.
This method requires one sensor system for every inking system.